Hydraulic cylinder assembly and method of manufacturing



NOV. 6, 195] s, B, MOLEQD 2,574,273

HYDRAULIC CYLINDER ASSEMBLY AND METHOD OF MANUFACTURING Filed Dec. 6, 1946 HID? STEWART B. MCLEOD Patented Nov. 6, 1951 HYDRAULIC CYLINDER ASSEMBLY AND METHOD OF MANUFACTURING Stewart B. McLeod, Deal-born, Mloin, auignor, by

means assignments, to Detroit Harvester Company, Detroit, Mich., a corporation of Michigan Application December I, 1946, Serial No. 714.380

The present invention relates to improvements in the construction or an hydraulic piston and cylinder assembly.

Recently suggested uses for lninulic cylinders have included the raising and lowering oi automobile windows or body tops of convertible automobiles. However such uses have required a compact relatively inexpensive and efllcient cylinder assembly which would not permit the hydraulic medium to leak past the piston nor through the various seams of the cylinder assembly. In order to lock the body of an automobile, it is necessarythat the windows, and the tops oi convertible automobiles, be maintained in their raised positions. This can be readily accomplished by trapping or locking the hydraulic fluid in the line after the windows, or top, are raised. I1, however, the hydraulic fluid can by-pass the piston or leak out-the seams of the cylinder assembly, the locking efiect is lost.

Previous attempts to make such highly efficient hydraulic cylinders have resulted in high precision and relatively costly cylinder and piston fittings which have prevented their general use with low cost equipment. In order to cut costs it has long been desirable to use inexpensive seamless steel tubing or electric resistance welded mandrel reduced steel tubing for the cylinder, and castings for the cylinder heads, so as to provide a cylinder assembly having parts that could be produced in quantity by mass production methods. In practice such materials have not proved satisfactory under the relatively high pressures required for normal operation. Regardless 01' how tightly the end of the cylinder is clamped around the head casting and sealing gasket, the difference in thermal expansion between the head casting and the walls of the tubing results in leakage around the cylinder head fittings under normal operating pressures. Likewise, conventional methods of preventing hydraulic fluid from bypassing the piston head have not been successful with the use of unpolished or unmachined stock tubing because of the usual surface irregularities on the inner side walls of such tubing.

Accordingly a principal object of the present invention is to provide an hydraulic cylinder assembly which is particularly characterized by its compactness of design, high efliciency in operation, and relatively low cost resulting from its ready manufacture by mass production methods. Another object of the present invention is to provide an hydraulic cylinder assembly of the character described which may be readily installed within the panels of a conventional auto- 2 Claims. (01. 809-2) 2 mobile body and in which the piston is adapted to withstand hydraulic pressure exerted or maintained selectively on either side thereof with sufliclent force to move the piston or to lock it against movement and without permitting the hydraulic fluid to bypass the piston.

Still another object is to provide an hydraulic cylinder of the character described and having an improved seam seal structure to prevent leaking of the hydraulic fluid and to enable the use 01 relatively low cost die castings 01 aluminum or zinc alloys or other materials for the head portion and the use of seamless tubing or electric resistance welded mandrel reduced tubing for the walls 01' the cylinder assembly.

Other objects 01' this invention will appear in the following description and appended claims,

reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

Fig. 1 is a section view of an hydraulic cylinder assembly embodying the present invention.

Fig. 2 is a cut-a-way view of one end of the cylinder of Fig. 1 and showing the detail of the seam seal construction.

Fig. 3 is a cut-a-way view of the other end of the cylinder of Fig. 1 and showing the detail of the seam seal construction.

Fig. 4 is an enlarged section view through the piston of the cylinder of Fig. 1.

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring to the drawings, an adaptation of the present invention is shown in relation to an hydraulic cylinder and piston assembly particularly adapted for use in raising or lowering automobile windows or the convertible motor vehicle tops by the use of ordinary non-corrosive hy-" draulic fluid as the pressurized medium to actuate the piston. However, a cylinder and piston embodying my invention is not limited to such uses but is readily adaptable for a wide variety of other uses requiring a highly efiicient and economical assembly wherein a movable piston is actuated by either a fluid or gaseous pressurizedmedium within a pressure chamber. The body II and the reduced steel tubing or seamless steel tubing the body portion II.

The term elastomeric" as employed in the present specification and following claims to describe the properties of the ring gasket is is a term of relatively recent usage, having its origin presumably in the plastic industry wherein it is in common acceptance as an adjective descriptive of the properties of elasticity, pliability, and fiexibility, and pertaining particularly to the elastic rubber-like properties of plastic materials which are readily deformable under ordinary atmospheric conditions of temperature and pressure and which, within the limits of their elasticity, readily regain their shapes when the deforming force is released. As thus defined, and as employed by those familiar with the plastics art, the term elastomeric is used herein.

Under ordinary circumstances, thedifference in the degree of thermal expansion between the steel tubing forming the body portion II and the head casting I! has prohibited the use of such materialsinpressurechamberscfthecharacter described. It is well known that aluminum or for sine alloys or comparable materials suitable for castings such as the head castings have a relatively higher coeflicient of thermal expansion thanthatofthesteelcommonlyusedinseamiess or resistance welded tubing. A necessary limitation on the initial "tightness" in the fit of the of normal diurnal temperature changes will give thefiaredends liapermanentexpandedset'even whenthe headcastings I! are againcooled. This allows the hydraulic fluid medium-to leak through the open spaces between the cylinder endportions It andtheheadcastings IL" I have discovered that by constructing the steel thermal seal ring II of the same material as the" hibing of the body portion I. or of material having a comparable coeilicient of thermal expansionandbyfittingsaidsealringilloosely' a'roundits portiono'ftheringway lisoastocontacttheadiacentinnerwallsofthecylindermd portions ll snuglyandtocompreltheelastomthe name I I against the seal ring formly distributed around the circumference d the elastomeric ring ll.

Aslongastheeiastomericrlnglasketllis properly supported and held in its proper shape. it is under suflicient compression to conform to minor irregularities within its area of contact with the cylinder head I! and cylinder end portion II. By virtue of its resiliency, gasket ll accommodates itself to normal thermal changu in the dimensions of the various elements forming the sealing chamber and forms a fluid-tight seal between its respective cylinder head If and thefiaredandcrimpedportionll ofthebody portion ll.

At the time of thermal expansion of the head castings II. the sealing efilciency of the elastomeric gaskets II is increased as a result of the increased compression thereof between the flared portions Ii and the head castings It. At the same time the flared portions II are subiect to receiving a permanent expanded set from the thermally expanded head castings It. By reason ofthelcosefitofthesealrings l1 armmdthe heads II, said heads I! are free to expand without breaking the rings ll. later when the head castings l2 cool and contract, the initial oompressionoftheelastomericgaaket iiissufleient tocompensate for whatever permanentexpandad setthe fiared portions II have acquired. Thus afilnd-orsas-tightsealbetweenthepartsinvolvedismaintainedatalltimesr,

Iha've foundthatsupportfor-theelsstomeric ringgasketilononesidealoneissuflctsntfor the purpose of providing a fluid-mt seal for an hydraulic cylinder anemblyto housed in raising the tops of the convertible automobile. Thusthedeviceshownhasonlyonethermlseal ring II for each cylinder head It. l'or other usesofanhydrauliccylinderrequiringhigher pressures,sealrings llsuchaslhavedescrihed areplacedonbothsidesoftheringsasket ll toprovideauniformdistrlbutionofpressureon both sides thereof. 7

Other features of either one or both of the cylinder headcastingsshownarethe ducts II for the hydraulic fiuid or pressurised medium med to operate the piston ll. the threaded openhms II to the ducts II which permit attachment d pressure feed lines to a source of the hydraulb fiuid, the dust wiperorseal it around the opening 21, the bolt hole It by which one end 0! the cylinder assembly may be pivotally attached to. a supporting member, and the packing gland it around the bearing borefor the piston rod 8|.

Inasmuch as minor surface irregularities in i tension on the inner surfaces of the side walls of the swck' tubing would prohibit the use or a conventional piston assembly, I have provided a piston I! v which is secured to a threaded end-of the 26 by the nut andwasher assembly 21 which, is

staked to the rod". The molded resilient covering 24,.secured to. the piston II and comprising a rubber or rubber-like plastic material,

essentially encloses the piston i! on all surfaces. The periphery of the resilient. pistoncovering 24 contacts the adjacent wall of the body portion I. of the cylinder by'means of -the two annular resilient lips 25 which extend angularly outward in opposite directions from the periphery oi the piston it and are held by virtue of their resiliency firmly against the inner walls oi the body portion II as shown inFig. 4.

When the pressureot an hydraulic fluid is exerted on either side of the piston ",the lip 25 on the same side thereof will be forced against theadjacent side walls 01' the body portion ll by the hydraulic pressure which acts equally'in -all directions. Thus the lip will conform to minor irregularities in the side wall of the cylinder II, and a fluidor gas-tight seal will be provided around the piston II. The greater the hydraulic pressure on the piston II and the lip 25. the more effective will be the seal. Upon locking the hydraulic fluid in the pressure line, a window, for example, operated by when the piston I! is moved to the right from- Near the end oi the piston stroke to the right, the spring '28v the position shown in Fig. 1.

is compressed between the piston l! and-cylinder head It, and the top is eased into its position: In certain conventional systems for raisingconvertible hy lar e quantities 6. saidpistoniisoastoprevent rattling of the mechanical linkages between the connecting rod 20 and the convertible top, aswell as between the linkages ot the top structure itself.

From; the foregoing it will'be seen that I- have provided a novel iorm oi hydraulic piston and cylinder assembly which is particularly characterized by its eillcientoperation, economy of manufac ure, and adaptation to manufacture in I. claim:

1. In a pressure cylinder; the combination ofa section of stock steel tubing. a plurality of die cast end-closure heads secured within the side-walls of the ends of said steel tubing. a

-means to form a seal between each oisaid die cast heads and the adjacent inner side-wall ot'the saidtubing and tocompensate for diti'erences in the thermal expansion 01 said die cast heads and said steel tubing and-comprise ing azringway on each oi said die cast heads. an elastomeric ring gasket tightly fitted within each 01-. said ringwayai a thermal seal ring formed 0! a material having substantially the same thermal expansion properties or the stock steel tubing'and mounted loosely within each of said ringways and in contact with the adjacent 'irmer side-wall oi the steel tubing and tightly adjacent one oi each oi said elastomeric I ring gaskets, each of said elastomeric ring gaskets being held in shape and under compression at its smaller periphery by its respective ringway and being held in shape and under compression at its larger periphery by said thermal seal ring.

2. In a pressure chamber comprising a tube and a head connected with the sidewalls oi the tube, a sealing means comprising an elas- I tomeric gasket dispo ed between the sidewalls of. the, tube and the head. and a thermal sealing member adjacent said gasket and composed of material having substantially the same thermal expansion properties as the tube, said thermal sealing member being tightly engaged with the sidewalls of the tube to provide a supple'mentary 'seal to prevent the escape of iluid drom' the pressure chamber throu h. openings .ibetween the sidewalls oi the tube and the head,

draulic cylinder means is-utilised.v J to raise the top'slightly beyond )thei-ipointoi;

a center of balance. "Beyond balance. the top falls otitsown weightand the header bar'otthe i 11. on top oi the automobile tag! or the spring becomes readilyapparent asa'meanstocheck thei'alloi' thetopand to prevent or the header bar in place.

Also in certain conventional convertible top arrangemens, provision is made to allow delight.

"windshield. adv'anhead having a stepped ringway rovided v ;tlierei.n totightly seat the said elastomeric gasket under co at the lower level and loosely guide the said thermal sealing ring at the upper level oi the step. the elastomeric gasheld in shape under compression at its smaller periphery by the ringway and at its larger periphery'by the thermal seal ring.

override in the stroke of the piston ll so as topermit application of a mechanical locking means to hold the top securely in theraised position. Upon mechanically locking the top in the raised position and releasing the hydraulic pressure, which drives the piston It to the right, Fig. 1, spring 28 takes up the slack of themride oithe stroke of piston ll and maintains Number s'rswsn'r n. amn on.

. I 3 'nnr'nanncns crran The following references areoi' record in the ille of this patent:

UNITED STATES PATENTS Name Date 2,089,609 Houghton Aug. 10, 193'! 2,230,286 Cotner Feb. 4, 1941 2,299,605 Greene Oct. 20, 1042 2,310,917 Le Grand Daly Feb. 18. 1043 Parsons July 2, 19M

by mass production methods. 

